It depends on your role. People in sales have it open all the time since it's a legitimate research tool for them.

Yep. Sales and biz dev people use LI constantly not necessarily for connecting, but learning about contacts.

If you’re considered valuable at your current company, instead of being a red flag it can help you get a raise or other benefits.

This. I would rather post on any other social media site at work than Linkedin. It's a major signal that the person is looking for work.

I can’t imagine working in a place toxic enough where:

1. That’s the default presumption (rather than someone doing networking for their current role)

2. Where “looking for another job” is a point of contention

Any good senior engineer should be keeping in touch with others in the industry. And good teams are made up of people with good communication skills who want to be there.

Especially the "Let me show you i have a open linkedin tab while screen sharing so you guys know i hate this place" move as if anyone cares.

No more such thing as commit to the company in western world anymore. Companies are definitely not commited to you.